Oxidation inhibited mineral oil



Patented Jan. 5, 1954 OXIDATION INHIBITED MINERAL OIL Walter J. Coppock, Ridley Park, Pa... assignor to Sun Oil Company, Philadelphia, Pa., a corporation of New Jersey No Drawing. Application June 23, 1950, Serial No. 170,059

chemical compounds having the desired inhibiting effect.

Many oxidation inhibitors have been proposed for lubricating oil. Among the best such inhibitors that have been proposed are certain alkylated phenols, particularly tertiary butyl sub-stituted phenols such as 2,6-ditertiary butyl-imethyl phenol. Such alkylated phenols are generally effective to inhibit oxidative deterioration of lubricating oil under ordinary conditions of use.

Certain types of lubricating oil, however, are used under unusually severe temperature conditions, e. g. 250-450" F.; and oxidation irmibitors which are suitable at ordinary temperature conditions of LISQ'E. g. 100-250 F., are frequently much less effective and therefore unsuitable when used in such lubricating oilunder such. severe temperature conditions.

Lubricating oil suitable for use under severe temperature conditions is required to have certain general specifications. For example, it must 'have relatively high flash point (A. S. T. M. D92- 46), e. g. 350 F. or above, and preferably above the highest temperature to which the oil is to be subjected; otherwise the oil will be too volatile for effective use under severe temperature conditions. Lubricating oil for certain specific applications involving severe temperature conditions must have additional specifications. For example, lubricating oil for use in automotive fluid couplings, Where temperatures of about 400 F. must be withstood, are generally required to have an U. viscosity at 100 F. within the ap roximate range 170-190, and S. U. viscosity at 210 F. not substantially less than 45. The present invention relates to the inhibition against oxidation of such lubricating oil and other lubricating oil suitable for use under severe temperature conditions.

. 6 Claims. (Cl. 25252) I have discovered that compounds having the formula where R is an aryl radical and R is selected from the group consisting of hydrogen, methyI, and ethyl radicals, are efiective oxidation inhibitors for lubricating oil used under severe temperature conditions.

Oxidation inhibitors for use according to the invention should be substantially non-volatile at the temperature at which the oil is used, i. e. they should have normal boiling points higher than the temperature of use of the oil. Phenoxy propylene oxide (1,2-epoxy-3-phenoxy propane, boiling point 452 F.) is an additive compound according to the invention which has high enough boiling point for severe temperature uses ordinarily encountered. Phenoxy propylene oxide is particularly advantageous for use according to the invention; for although phen-oxy propylene oxide, as an oxidation inhibitor for oil under ordinary temperature conditions of use, is inferior to at least one Widely used alkylated phenol oxidation inhibitor of the prior art, it has been found that on the other hand phenoxy propylene oxide is distinctly superior to that same alkylated phenol oxidation inhibitor as an inhibitor for oil under severe temperature conditions of use.

The amount of additive compound according to the invention used in a given amount of lubricating oil will Vary according to the degree'of oxidation inhibition desi1 'ed. Generally, satisfactory results are'obtained with 0.01-2100weight percent of additive.

The following example illustrates the invention:

The oil tested in this example was a solvent-refined, dewaxed, acid-treated, and clay-treated distillate from mixed-base crude petroleum, the distillate having an S. U. viscosity at F. of about 185 and a viscosity index of about 90. Two samples of this oil were tested for oxidation stability under severe temperature conditions by subjecting each to a temperature of 400 F. in an oven for hours, air being passed through the sample during this period at the rate of two bubbles per second. Before and after the oxidation period, the amount of naphtha-insoluble material in each sample and the S. U. viscosity at 210 F. of each sample were determined.

Sample No. 1 contained one weight percent of 2,6-ditertiary butyll-methyl phenol as oxidation inhibitor, and Sample No. 2 contained one Weight 3 percent 01 phenoxy propylene oxide as oxidation inhibitor. The following table shows the increase in naphtha-insoluble content and in 210 F. viscosity for each sample during the oxidation 4, major proportion of mineral lubricating oil suitable for use under severe temperature conditions; and a minor proportion constituting an oxidation inhibiting quantity of a compound having period 6 the formula R-OCH:CH-CHR' Percent Percent Increase in Increase in Sample i qggwhere R is an aryl radical and R' is selected from Materials 210 F. the group consisting of hydrogen and methyl and ethyl radicals. 1. 1.3 78 '2. Composition according to claim 1 wherein 2 said oil has a flash point of at least about 350 F. 3. Composition according to claim 1 wherein The above results Show lubrlcatlng O11 lIlpercent of said aroxy epoxy alka ne in hibited with 2,6-ditertiary butyl-4-methyl phenol the composition is about undergoes greater oxidative deterioration under Composition according to claim 1 wherein severe temperature conditions than does the same said aroxy epoxy alkane is 1,2 epoXy 3 phenoXy oil inhibited with phenoxy propylene oxide. propane On the other hand, lubricating Oi]. 5 The method of lubricating metal parts with fi- Y butyl-l-methyl phenol which comprises: contacting such parts with erally undergoes less oxidative deterioration unmineral lubricating oil at a temperature in the der ordinary temperature conditions of use than range fro to F" Said 011 containing do the S Oil inhibited With p 'l y P a minor proportion constituting an oxidation inpylene oxide. For example, an oil havm pr hibiting quantity of a compound having the forerties generally like those of the oil tested inltl'ae, mula, example above, but having S. U. viscosity at 0 F. of about 160, was found to be more stable in R o CH2 R the turbine oil oxidation stability test (A. S. T. M. 0 I D943-4'7T), which is conducted at 203 F., when where R is an aryl radical and R is selected from inhibited with 2,6 ditertiary butyl--methyl the group consisting of hydrogen and methyl phenol than when inhibited with phenoxy pro13Y1- and ethyl radicals.

ene oxide. 6. A composition consisting essentially of a Thus, it iS seen that the efiectiveness Of lubrimajor proportion of mineral lubricating oil and eating oil oxidation inhibitors depends on the i o prgportion constituting an oxidation conditions to which the oil is subjected during hibiting quantity of a compound having the foruse, and that phenoxy propylene oxide gives sul perior results in oil used under severe temperature conditions, as compared with a prior art oxidation inhibitor, such as 2,6-ditertiary butyl-l- 4O 0 methyl h l, where R is an aryl radical and R is selected from Although, in the preceding example a phenoxy the group c nsi tin f y n n m hyl n epoxy propane is used as an example of the adethyl radicals. ditive employed, similar results may be obtained WALTER J. COPPOCK. when other additive compounds within the scope of the invention are used. Such compounds may References clted m the file of this Patent be prepared by any suitable method, e. g., by re- UNITED STATES PATENTS acting at about 100 C. an excess of an epoxy chloro alkane such as epichlorohydrin, or 1- g ggz fii Jan 5 chloro-2,3-epoxy butane, etc. with an aqueous 1 6 Myer 1939 solution of an alkali metal salt of phenol or other 2221818 slagh Nov 1940 aryl hydroxy compound such as cresol, methyl 2263664 Wassol; Nov 1941 isopropyl phenol, bromophenol, nitrophenol, 2362516 Wasson 1944 ggfiy 2,438,468 Wasson Mar. 23, 1948 1. A lubricating composition comprising: a 

1. A LUBRICATING COMPOSITION COMPRISING: A MAJOR PROPORTION OF MINERAL LUBRICATING OIL SUITABLE FOR USE UNDER SEVERE TEMPERATURE CONDITIONS; AND A MINOR PROPORTION CONSTITUTING AN OXIDATION INHIBITING QUANTITY OF A COMPOUND HAVING THE FORMULA 